When your stepsister has a boyfriend: Yui Nagase

I've always thought that anyone who looks at their own stepsister in a sexual way is a crazy person. Until my stepsister got a boyfriend. I don't care what my stepsister does, and I'm more comfortable when we don't have much contact or conversation. That was the distance between me and my stepsister. But when I heard her on the phone with her boyfriend or found a cute pair of underwear that wasn't there before, I realized that a different feeling was starting to grow inside me.